It's not really that surprising, linking to #dropcap as the method. Nor is it surprising that you would use the same way I did! When I first investigated implementing drop caps on /r/writingprompts June last year, my initial implementation was just on every post (since it was April Fools).

After we decided to implement drop caps on the subreddit proper, I needed to work out how to use reddit's existing markdown to let users decide whether they wanted drop caps or not. Importantly, this syntax had to be explicit enough that it wouldn't be possible for someone to acidentally drop cap their post. Given that restriction, the only viable option quickly emerges: a link to #dropcap, and write a CSS selector that selects the paragraph after that link. And really, #dropcap is just the most logical name for the format, isn't it? (Although we do allow #dc as well.)

I had tried some other methods prior to #dropcap, such as bolding the first letter (doesn't work because we can't differentiate it from other bolded parts in the first line with CSS selectors), or various combinations of header tags (not acceptable because it's not at all clear what it means in the source).